Orthogonal frequency division multiplexing (OFDM) is a form of multiplexing that distributes data over a number of carriers that have a very precise spacing in the frequency domain. The precise spacing and partially overlapping spectra of the carriers provides several benefits such as high spectral efficiency, resiliency to radio frequency interference and lower multi-path distortion. Due to its beneficial properties and superior performance in multi-path fading wireless channels, OFDM has been identified as a useful technique in the area of high data-rate wireless communication, for example wireless metropolitan area networks (MAN). Wireless MAN are networks to be implemented over an air interface for fixed, portable, and mobile broadband access systems.
In an OFDM system, a pilot channel is usually used to obtain transmission channel information to enable coherent detection. One type of pilot channel is a common pilot channel that is used by all transmitters and receivers in a telecommunication cell. Another type of pilot channel is a dedicated pilot channel that is used by transmitters and can only be detected by receivers to which the pilot channel is directed. These two types of pilot channels are currently applied in different systems.